First define the variables:
c = amount of children
a = amount of adults
Next create the equations to satisfy the conditions:
1) Total group is 12 people:

2) Total cost is $100 with adults costing $10 and children being $6:

Answer:
98
Step-by-step explanation:
Add them all up. 60+20= 80+18 = 98.
The correct answer to your question is 8.